- A chemical that experts believe may be
able to treat the brain disease CJD has produced spectacularly successful
results in mice.
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- A team from the Institute for Animal
Health in Edinburgh inoculated mice that had been infected with scrapie
- a disease of the brain similar to CJD - with the chemical pentosan polysulphate
(PS).
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- Animals injected with one milligram of
PS appeared to be completely protected against the scrapie. They died from
unrelated causes between 500 and 707 days after they were "inoculated"
with the drug.
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- Mice who received no PS died of scrapie
within 428 days.
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- The incubation period for scrapie was
increased by up to 66% for doses of PS as small as 250 micrograms.
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- The researchers say further studies are
now needed to test whether PS can reduce the risk of CJD.
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- Dr Moira Bruce, head of pathology at
the institute, said the previous research had shown PS to be effective
in treating scrapie, but not in such small, single doses.
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- The Edinburgh research is also the first
time that animals have been successfully treated after being infected.
Previously, they were inoculated before being infected with the disease.
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- Dr Bruce said: "This research shows
that a very small dose can produce really quite a dramatic effect if you
get the time right."
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- Dr Bruce warned, however, that much more
work was needed before the drug was used on humans. She said there would
be problems identifying which people were carrying the CJD infection soon
enough to ensure PS could work.
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- Spongy texture
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- Thirty-five people in the UK have been
diagnosed as suffering from new variant CJD since scientists said in March
1996 that they had evidence it could be contracted by eating beef from
animals suffering from BSE, or mad cow disease.
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- CJD, like BSE and scrapie, causes the
brain to develop a spongy texture known as spongiform encephalopathy.
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- At present, there is no treatment to
slow or halt nv-CJD, and the diagnosis is usually made when patients are
terminally ill.
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- During the long incubation period when
there are no symptoms, there is a risk that the infection may be transferred
by blood transfusion, treatment with blood products, transplantation or
reuse of surgical instruments.
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- PS is already licensed in the US for
the treatment of a form of cystitis.
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- Microbiologist Dr Stephen Dealler, of
Burnley General Hospital, is working on a treatment for CJD in humans.
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- He said the Edinburgh research was "very
exciting".
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- "Pentosan does not just prevent
the disease from progressing in animals, it actually gets rid of it,"
he said.
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- "The potential importance of this
drug to humans cannot be underestimated."
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- Drug Offers Hope On CJD/BSE
Front
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- By Alan MacDermid www.theherald.co.uk
1-9-99
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- Scientists have found that a drug might
be effective in curbing or protecting against the human form of so-called
mad cow disease.
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- Researchers at the Institute for Animal
Health in Edinburgh called for further trials of the drug, pentosan polysulphate,
which is used in the US to treat cystitis.
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- They tested it on mice seven hours after
they had been infected with scrapie, a sheep-borne form of transmissible
spongiform encephalopathy thought to be the origin of Creutzfeldt-Jakob
Disease and its human equivalent, new variant CJD.
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- Some mice survived longer than mice that
did not get the drug; others did not succumb to the disease at all.
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- The findings are reported today in the
Lancet, and last night it emerged that scientists advising the Government
on CJD will consider the use of pentosan on Monday. The Spongiform Encephalopathy
Advisory Committee will look at all the evidence and may then make a recommendation
to Ministers.
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- Thirty-five people in Britain have been
diagnosed as having the invariably fatal nvCJD since scientists said in
1996 that it could be contracted by eating beef infected by mad cow disease.
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- The extent of the future problem is unclear
because of the long incubation period associated with the disease.
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- The mice were a special breed genetically
engineered to be susceptible to the sheep disease.
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- The researchers found that 250 micrograms
of pentosan increased the average incubation period of one scrapie strain
by up to 66%.
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- A milligram of pentosan protected mice
completely from another strain.
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- The Lancet report states: "This
represents at least a hundred-fold reduction in the sensitivity of these
mice to infection. Although direct testing of the efficacy of pentosan
polysulphate in reducing susceptibility to nvCJD is not possible, further
animal studies are essential to examine the possible use of the drug for
risk reduction."
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- One of the Edinburgh researchers, Dr
Moira Bruce, said yesterday: "We are at a fairly early stage in considering
a practical application. What we have shown is that a single low dose given
very shortly after exposure can extend the incubation period and in some
cases protect the animals.
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- "We don't know enough about the
action of this drug yet to the extent of suggesting how it might be used.
The problem with CJD is that individuals are normally infected long before
they develop any clinical indications, and the effect of the drug is in
the early stages. So we would have the problem of knowing when to give
it. However there have been other animal studies in which large doses were
given prior to infection and proved effective.
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- "We do not know if it would be effective
in humans, we aren't sure about side-effects, and we have not tried it
on BSE itself."
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- Diseases such as CJD are thought to spread
by a rogue form of protein turning other proteins "bad" in a
chain reaction. Pentosan latches on to the proteins, called prions, and
stops them affecting their neighbours.
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- Dr Stephen Dealler, who has reviewed
several studies of pentosan's effects, said: "This is a nettle that
needs to be grasped. We may actually have a drug which can prevent humans
becoming infected. The Government must do something about it immediately."
- Jan 8
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- http://www.theherald.co.uk/news/archive/../../home_frame.html
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